Complete the following tasks to unlock the corresponding achievement. To view 
your achievements and stats in Steam, select "Community", then "My profile", 
then "View all my games", then the game and view stats.

Achievement                 Description
---------------------------------------------------
Bulletproof Vest          - Win against Raid Engine on difficulty 9 or up.
Bulletproof Vest          - Win against Raid Engine on any difficulty.
Bulletproof Vest          - Win against Raid Engine on difficulty 7 or up.
Do I Seem Heavier To You? - Win against Gravity Driller on difficulty 7 or up.
Do I Seem Heavier To You? - Win against Gravity Driller on any difficulty..
Do I Seem Heavier To You? - Win against Gravity Driller on difficulty 9 or up.
Don't Open That Door      - Win against One-Way Doormasterr on difficulty 9 or up.
Don't Open That Door      - Win against One-Way Doormaster on difficulty 7 or up.
Don't Open That Door      - Win against One-Way Doormaster on any difficulty.
I Like Trying New Things  - Win against Experimentalist on difficulty 9 or up.
I Like Trying New Things  - Win against Experimentalist on difficulty 7 or up.
I Like Trying New Things  - Win against Experimentalist on any difficulty.
What A Ninny              - Win against Shield Ninny on any difficulty.
What A Ninny              - Win against Shield Ninny on difficulty 7 or up.
What A Ninny              - Win against Shield Ninny on difficulty 9 or up.
You Guys Are Mean         - Win against Tag Teamer on difficulty 9 or up.
You Guys Are Mean         - Win against Tag Teamer on difficulty 7 or up.
You Guys Are Mean         - Win against Tag Teamer on any difficulty.